The present invention relates an offset printing machine with variable format.
It is known that offset printing machines comprise an inking device and a dampening device for applying a layer of ink and a layer of a dampening solution, generally water, on the surface of at least one inking roller itself in contact with a plate cylinder. A blanket cylinder is mounted tangentially to the plate cylinder to effect printing on a web or sheet advancing between this blanket cylinder and an impression cylinder applied under pressure thereagainst.
Such a known machine, provided for successively printing several colours on the same web, comprises a plurality of superposed printing assemblies, each of these printing assemblies comprising a plate cylinder and a blanket cylinder mounted tangentially to each other in the same horizontal plane. The pairs of plate and blanket cylinders are thus superposed and are all borne by a unit adapted to be displaced in the transverse direction, i.e. perpendicularly to the direction of advance of the printed web, so as to be removable from the frame of the machine and replaced by another similar unit bearing plates corresponding to a fresh printing operation. Such a machine, although is presents incontestable advantages as far as the convenience of replacing the plate cylinders is concerned, is, however, not adapted to printing in different formats which requires relatively frequent replacements of the plate cylinders, as a function of the desired format of print.